I suspect that the eternal problem will be that of context.

Back when Google started out, they bet the farm on the idea that more links pointing to a document meant that said document was informative.

These days though, i wonder if what we are looking for is more hair. That what we are looking for depends on a context that can't be properly included in the search terms used.

On top of this "naive" metrics like link counts are no longer a viable measure for what to elevate to the top of the search results.